Wafer-adhering adhesive tape

ABSTRACT

A wafer-adhering adhesive tape, which has, on a surface of a base, a radiation-curable removable adhesive layer, and if necessary a die-bonding adhesive layer in order, wherein the radiation-curable removable adhesive layer is mainly composed of an acrylic-series copolymer having, in a principal chain, at least a radiation-curable carbon-carbon double bond containing group, a hydroxyl group, and a group containing a carboxyl group, respectively, and the radiation-curable removable adhesive layer has a gel fraction of 60% or greater.

TECHNICAL FIELD

The present invention relates to an adhesive tape that is provided witha removable adhesive agent layer on one side of a base film.

BACKGROUND ART

An assembling process of a semiconductor device, such as an IC or thelike, comprises the steps of: cutting and separating (dicing) asemiconductor wafer and the like into respective chips, afterpatterning; mounting the chips on a substrate or the like; and sealingthem with a resin or the like.

In the dicing step, a semiconductor wafer is adhered and fixed by anadhesive tape in advance, and then it is diced along a chip shape. Inthe mounting step, the chip is peeled off (picked up) from the adhesivetape and then fixed on a substrate or the like with an adhesive agentfor adhering and fixing.

The tapes used for the above purposes include a usual pressure-sensitiveadhesive-type tape, and a tape having a reduced adhesive force when itis hardened or cured by radiation, such as ultraviolet (UV) rays,electronic rays, and the like. Both of these types of tapes are requiredto have sufficient adhesive force so that the tape is not peeled offfrom the wafer upon dicing, and they are also required to have peelingcapability to be easily peeled off from the wafer upon picking up.

Further, in the mounting step, sufficient adhesive force is requiredbetween the chip(s) and the substrate and the like.

There are suggested a variety of adhesive or adhesion tapes that areequipped with both of the function of a dicing adhesive tape used in theabove process, and the function of an adhesive on a substrate and thelike, which tapes are improved in the coating workability of theadhesive, and which simplify the whole process.

These adhesive tapes enable a so-called direct die bonding for, afterdicing, picking up a chip with a removable adhesive layer adhered on therear side of the chip, mounting the chip on a substrate or the like, andcuring and adhering the chip by heating or the like. By these adhesivetapes, the coating process of an adhesive can be omitted.

However, the removable adhesion agent or adhesive agent used for theseadhesive tapes is in a coating liquid state with low viscosity and lowwettability to a tape base, and thus it has the problem of poor yield.Further, the above adhesion or adhesive agent is low in adhesionstrength, compared with an existing adhesive or bonding agent for diebonding. Thus it is difficult to obtain reliability from the aboveadhesion or adhesive agent.

As means to obtain adhesion reliability and provide dicing performance,it is proposed to use a laminate of a die bonding adhesive layer and adicing tape. However, this laminate-type tape has the problem that it isdifficult to control the peeling ability between the adhesive and thedicing tape. A die bonding adhesive with high adhesion reliabilitygenerally requires heat adhesion upon temporarily fixing it to a wafer.However, the laminate-type tape has the problem of increase of peelingability between the dicing tape and the die-bonding-sheet adhesive layerdue to such a heat adhesion, thereby causing a raise of the pickupfailure ratio after the dicing.

Further, it is also proposed that a die bond sheet is heat-adhered to awafer in-advance, and a dicing tape is laminated to the die bondingadhesive layer adhered to the wafer, before use. Also, in this case, asurface protective tape for back-grinding is usually bonded to a side ofthe wafer on which no die bonding sheet or dicing tape is bonded. Topeel the surface protective tape from the wafer by lowering the adhesiveforce of the surface protective tape, a heat treatment is generallycarried out. The heating temperature is generally about 40° C. or more,for example, about 60° C. Similarly to the above, this causes theproblem of increased peeling force between the die bonding adhesivelayer and the dicing tape.

DISCLOSURE OF THE INVENTION

The present invention resides in a wafer-adhering adhesive tape, whichhas a radiation-curable removable adhesive layer on a surface of a base,wherein the radiation-curable removable adhesive layer is mainlycomposed of an acrylic-series copolymer having, in a principal chain, atleast a radiation-curable carbon-carbon double bond containing group, ahydroxyl group, and a group containing a carboxyl group, respectively,and the radiation-curable removable adhesive layer has a gel fraction of60% or greater.

Further, the present invention resides in a wafer-adhering adhesivetape, which has a radiation-curable removable adhesive layer and adie-bonding adhesive layer, in this order, on a surface of a base,wherein the radiation-curable removable adhesive layer is mainlycomposed of an acrylic-series copolymer having, in a principal chain, atleast a radiation-curable carbon-carbon double bond containing group, ahydroxyl group, and a group containing a carboxyl group, respectively,and the radiation-curable removable adhesive layer has a gel fraction of60% or greater.

Other and further features and advantages of the invention will appearmore fully from the following description.

BEST MODE FOR CARRYING OUT THE INVENTION

According to the present invention, there are provided the followingmeans:

-   -   (1) A wafer-adhering adhesive tape, having a radiation-curable        removable adhesive layer on a surface of a base, wherein the        radiation-curable removable adhesive layer is mainly composed of        an acrylic-series copolymer having, in a principal chain, at        least a radiation-curable carbon-carbon double bond containing        group, a hydroxyl group, and a group containing a carboxyl        group, respectively, and the radiation-curable removable        adhesive layer has a gel fraction of 60% or greater;    -   (2) A wafer-adhering adhesive tape, having a radiation-curable        removable adhesive layer and a die-bonding adhesive layer, in        this order, on a surface of a base, wherein the        radiation-curable removable adhesive layer is, mainly composed        of an acrylic-series copolymer having, in a principal chain, at        least a radiation-curable carbon-carbon double bond containing        group, a hydroxyl group, and a group containing a carboxyl        group, respectively, and the radiation-curable removable        adhesive layer has a gel fraction of 60% or greater; and    -   (3) The wafer-adhering adhesive tape according to the above        item (1) or (2), wherein the ratio of carbon-carbon double bonds        contained in the radiation-curable removable adhesive layer is        0.5 to 2.0 meq/g (milliequivalents/gram).

Herein, the term “being mainly composed of” means that a main componentof a removable adhesive component in the radiation-curable removableadhesive layer, which layer is comprised of the removable adhesivecomponent, a hardening agent and a polymerization initiator, is theacrylic-series copolymer having a carbon-carbon double bond containinggroup, a hydroxyl group, and a carboxyl group, respectively. Further, inthe adhesive tape of the present invention, 60% by mass or more of theradiation-curable removable adhesive layer is generally composed of theacrylic-series copolymer having a carbon-carbon double bond containinggroup, a hydroxyl group, and a carboxyl group, respectively.

Further, herein, the “removable adhesive” means an agent capable ofadhering and being removed after treatment such as curing, while an“adhesive” means an agent capable of adhering only. For example, the“radiation-curable removable adhesive” means a removable adhesivecapable of being removed or pealed off by hardening by irradiation ofradiation such as UV, after application of the removable adhesive to awafer and the like.

The present invention will be described in detail below.

The present inventors have keenly studied to solve the above-describedproblems in the conventional adhesive or adhesion tapes. As a result,the present inventors found that defective picking-up does not occur,while maintaining sufficient adhesion reliability, by using an adhesivetape that comprises an adhesive or adhesion composition, which is mainlycomposed of an acrylic-series polymer having at least aradiation-curable carbon-carbon double bond containing group, a hydroxylgroup, and a group containing a carboxyl group, respectively, in aprincipal chain, and which composition has a gel fraction of 60% orgreater; and, if necessary, further laminating a die-bonding adhesivelayer with the above adhesive tape. The present invention has beenaccomplished based on this finding.

The wafer adhering adhesive tape of the present invention can be made byforming a radiation curable removable adhesive layer on a base surface,in which the removable adhesive layer is mainly composed of theacrylic-series copolymer having at least a radiation curablecarbon-carbon double bond containing group, a hydroxyl group and acarboxyl group-containing group, respectively, in the principal chain,and in which the adhesive layer has a gel fraction of 60% or greater.Further, in addition to the radiation curable removable adhesive layer,a die-bonding adhesive layer may be form on the base surface, and it ispreferred to form the radiation curable removable adhesive layer and thedie-bonding adhesive layer, in order, on the base surface.

The acrylic-series copolymer (hereinafter, referred to as “acryliccopolymer (A)”) having at least a radiation curable carbon-carbon doublebond containing group, a hydroxyl group, and a group containing acarboxyl group, respectively, in the principal chain, which copolymercan be used in the present invention, may be any one prepared by anymanner. For example, the acrylic copolymer (A) can be obtained, bysubjecting a copolymer (A1), which comprises a (meth)acrylic acid ester,a hydroxyl group-containing unsaturated compound, a carboxylgroup-containing unsaturated compound, and the like, to additionreaction with a compound (A2) that has a functional groupaddition-reactive to a functional group in the copolymer (A1) and thathas a carbon-carbon double bond, in which a carbon chain of thecopolymer (A1) is to be a principal chain.

As the (meth)acrylic acid ester, included are, for example, hexylacrylate, n-octyl acrylate, isooctyl acrylate, 2-ethylhexyl acrylate,dodecyl acrylate, decyl acrylate, each having 6 to 12 carbon atoms, ormonomers having 5 or less carbon atoms, such as pentyl acrylate, n-butylacrylate, isobutyl acrylate, ethyl acrylate, and methyl acrylate, ormethacrylates like these. In this case, as the number of carbon atoms ofmonomers increases, the glass transition temperature becomes lower,thereby enabling manufacture of monomers of a desired transitiontemperature. Further, besides the glass transition temperature, for thepurpose of enhancing compatibility and various performances, a lowmolecular compound having a carbon-carbon double bond, such as vinylacetate, styrene, and acrylonitrile, can be blended within the range of5% by mass or less.

Examples of the hydroxyl group-containing unsaturated compound include2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropylacrylate, 2-hydroxypropyl methacrylate, and the like.

Examples of the carboxyl group-containing unsaturated compound includeacrylic acid, methacrylic acid, and the like.

As a functional group in the above-described compound (A2) having anaddition reactive functional group and a carbon-carbon double bond, in acase that the functional group in the copolymer (A1) is a carboxyl groupor a cyclic acid anhydride group, included are a hydroxyl group, anepoxy group, an isocyanato group, and the like; or in a case that thefunctional group in the copolymer (A1) is a hydroxyl group, included area cyclic acid anhydride group, an isocyanato group, and the like; or ina case that the functional group in the copolymer (A1) is an aminogroup, included is an isocyanato group, and the like. Specific examplesof the compound (A2) include acrylic acid, methacrylic acid, cinnamicacid, itaconic acid, fumaric acid, phthalic acid, 2-hydroxyalkylacrylates, 2-hydroxyalkyl methacrylates, glycol monoacrylates, glycolmonomethacrylates, N-methylol acrylamide, N-methylol methacrylamide,allyl alcohol, N-alkylaminoethyl acrylates, N-alkylaminoethylmethacrylates, acrylamides, methacrylamides, maleic anhydride, itaconicanhydride, fumaric anhydride, phthalic anhydride, glycidyl acrylate,glycidyl methacrylate, allyl glycidyl ether, and polyisocyanatecompounds in which isocyanato groups are partially urethanated with amonomer having a hydroxyl group or carboxyl group and aphotopolymerizable carbon-carbon double bond.

In the synthesis of the acrylic-series copolymer (A), when carrying outcopolymerization by solution polymerization, a ketone-series,ester-series, alcohol-series, or aromatic-series solvent can be used asan organic solvent. Among these, a preferable solvent is a usual goodsolvent for an acrylic-series polymer, which solvent has a boiling pointof 60 to 120° C. Examples of the preferable solvent include toluene,ethyl acetate, isopropyl alcohol, benzene methylcellosolve,ethylcellosolve, acetone, methyl ethyl ketone, and the like. As apolymerization initiator, use may be generally made of a radicalgenerating agent of azobis-series, such as α,α′-azobisisobutyronitrile,and organic peroxide-series, such as benzoylperoxide. At this time, acatalyst, a polymerization inhibitor can be optionally added, ifnecessary. In this way, it is possible to obtain an acrylic-seriescopolymer (A) with a desired molecular weight, by controlling apolymerization temperature and a polymerization time, and then carryingout an addition reaction at a functional group. As for the control ofthe molecular weight, it is preferred to use a mercaptan-series orcarbon tetrachloride-series solvent.

Additionally, this copolymerization is not limited to a solutionpolymerization, but it may also be performed in other ways such as bulkpolymerization, suspension polymerization, and the like.

As mentioned in the above, the acrylic-series copolymer (A) can beobtained. In the present invention, the mass average molecular weight ofthe acrylic-series copolymer (A) is preferably about 300,000 to about1,000,000. If the molecular weight is too small, the cohesive force byirradiation of a radiation becomes lesser, thus a misalignment ofelements (chips) may occur easily upon dicing the wafer, and imagerecognition may be difficult. Further, to prevent this misalignment ofelements as much as possible, it is preferable that the molecular weightis 400,000 or more. If the molecular weight is too large, there is apossibility of gelation upon synthesis and coating. Further, as forproperties of the copolymer, since the glass transition temperature islow, the flowability of the removable adhesive after irradiation of aradiation is not sufficient in a case of irradiation of a radiation notin a pattern shape but entirely, even if the molecular weight is large.Thus, although there occurs no such problems that an interval betweenelements is insufficient after stretching or that it is difficult torecognize an image upon picking up, the molecular weight is morepreferably 900,000 or less. Herein, the molecular weight in the presentinvention means a mass average molecular weight in terms of polystyrene.

Further, in the present invention, an amount to be introduced of aphotopolymerizable carbon-carbon double bond in the acrylic-seriescopolymer (A) may be varied according, for example, to use conditionsthereof such as a UV irradiation amount and the like, and it is notlimited, as long as it reaches an amount to give the effect ofsufficiently lowering the adhesive force after radiation curing. Theamount of the photopolymerizable carbon-carbon double bond to beintroduced is preferably 0.5 to 2.0 meq/g, more preferably 0.8 to 1.5meq/g. If the double bond amount is too small, the effect of reducingthe adhesive ability after irradiation of a radiation becomes smaller.If the double bond amount is too large, the flowability of the removableadhesive after irradiation of a radiation is insufficient, thereby tomake insufficient intervals between the resultant elements afterstretching and make it difficult for each element to recognize an imageupon picking up, in some cases. In this case, further, theacrylic-series copolymer (A) itself may be insufficient in stability andmay be made difficult to manufacture.

In the present invention, the gel fraction of the radiation-curableremovable adhesive layer can be controlled by the average molecularweight of the acrylic-series copolymer (A) and the amount of thehardening agent to be blended. The gel fraction is 60% or greater, andmore preferably 80% or greater. If the gel fraction is too small, theremovable adhesive component may be slightly moved on the contactinterface, thus making it difficult to obtain stability on the peelingforce with the lapse of time.

Further, the acrylic-series copolymer (A) has a hydroxyl group and acarboxyl group-containing group, each of which is unreacted, in theprincipal chain. It is preferable that the acrylic-series copolymer (A)has a hydroxyl group so that a hydroxyl group value is from 5 to 10,more preferably from 20 to 70, since the adhesive ability afterirradiation of a radiation is reduced, to thus further decrease the riskof picking-up mistakes. Further, it is preferable that theacrylic-series copolymer (A) has a carboxyl group so that an acid valueis from 0.5 to 30, since the tape recovery (restoration) ability isimproved, to thus make it easy to cope with a tape housing-typemechanism for a used tape. The acid value is more preferably 1 to 10. Inthe meanwhile, if the hydroxyl group value of the acrylic-seriescopolymer (A) is too low, the adhesive ability after irradiation of aradiation is not sufficiently reduced, or if too high, the flowabilityof the removable adhesive after irradiation of a radiation is damaged.Further, if the acid value is too low, the tape recovery ability is notsufficiently improved, or if too high, the flowability of the removableadhesive is damaged.

Further, in case of hardening the radiation-curable removable adhesivelayer for use in the present invention by ultraviolet irradiation, as anadditional component, if necessary, use can be made of a photopolymerization initiator, such as isopropyl benzoin ether, isobutylbenzoin ether, benzophenone, Michler's ketone, chlorothioxanthone,dodecyl thioxanthone, dimethyl thioxanthone, diethyl thioxanthone,benzyl dimethyl ketal, α-hydroxycyclohexyl phenyl ketone,2-hydroxymethylphenylpropane, and the like. The amount of the photopolymerization initiator to be blended is preferably 0.01 to 5 massparts, to 100 mass parts of the acrylic-series polymer.

Further, the radiation curable removable adhesive layer may contain, ifnecessary, another additional component including, for example, ahardening agent such as a polyisocyanate compound and the like. Theamount of the hardening agent to be blended is preferably 0.5 to 10 massparts, to 100 mass parts of the acrylic-series polymer that is the maincomponent.

The thickness of the radiation-curable removable adhesive layer ispreferably 5 to 50 μm.

The base that can be used in the present invention may be a film of anymaterial having a radiation transmission ability. Examples of the filminclude those made, for example, of a homopolymer or copolymer of anα-olefin, such as polyethylene, polypropylene, an ethylene/propylenecopolymer, polybuten, an ethylene/vinyl acetate copolymer, anethylene/acrylate copolymer, or an ionomer; an engineering plastic, suchas polyethylene terephthalates, a polycarbonate, or poly(methylmethacrylate); or a thermoplastic elastomer, such as polyurethane,styrene/ethylene/buten, or a penten-series copolymer. Alternately, amixture or double or higher layer of two or more kinds selected from theabove compound group may be used.

The thickness of the base film to be used is preferably 50 to 200 μm.

By laminating the thus-obtained adhesive tape and a die-bondingadhesive, it is possible to make the wafer-adhering adhesive tape withhigher performance. As the die-bonding adhesive, an acrylic/epoxy-seriesdie bonding adhesive or the like can be used. By heat adhering thewafer-adhering adhesive tape to a semiconductor wafer, sufficientadhesive ability is obtained in the dicing step so not to peel off orremove the wafer, the die-bonding adhesive layer, the radiation-curableremovable adhesive layer, and the base film each other. On the otherhand, when picking up, the removable adhesive layer can be easily peeledoff from chips attached to the die-bonding adhesive layer via radiationhardening.

Further, the similar effects can be exhibited by adhering the adhesivetape of the present invention, to the die-bonding adhesive layer side ofthe wafer with the die-bonding adhesive film attached thereto.

The peeling force of the die-bonding adhesive layer and theradiation-curable removable adhesive layer upon dicing is preferably 0.5to 10 N/25 mm, and the peeling force between the chip attached to thedie-bonding adhesive layer and the tape attached with the removableadhesive layer after irradiation of a radiation is preferably 0.5 to0.05 N/25 mm.

In one preferable example of the present invention, the radiationcurable removable adhesive layer and the die-bonding adhesive layer areformed on the surface of a base, in this order from the base side. Inthe die-bonding adhesive layer in the present invention, for example, abonding adhesive gent which is usually used for die-bonding, such as afilm-like bonding adhesive mainly composed of an epoxy resin, can beused. The thickness of the die-bonding adhesive layer is preferably 5 to50 μm.

The wafer-adhering adhesive tape of the present invention has sufficientadhesive ability that the radiation-curable removable adhesive layer isnot peeled off from a die-bonding adhesive layer and a wafer, whendicing; it allows easy removal of the removable adhesive layer and achip attached to the die-bonding adhesive layer by radiation andhardening, when picking up; and it gives sufficient adhesive abilitybetween the resultant chip and a substrate or the like, when mounting;thereby it enables a so-called direct die bonding

Further, the wafer-adhering adhesive tape of the present invention canbe used as a dicing tape upon dicing, and it can be used with theadhesive layer easily peeled off upon mounting, thereby to enable adirect die-bonding, and the wafer-adhering adhesive tape is excellent instorage stability. Further, when a die bonding sheet is heat-adhered toa wafer in advance and a dicing tape is laminated onto a die-bondingadhesive layer bonded to the wafer before use, the wafer-adheringadhesive tape of the present invention can be preferably used as theabove dicing tape. Further, according to the wafer-adhering adhesivetape of the present invention, an interval between elements issufficiently made after stretching, while obtaining the effects ofreducing adhesive force after radiation hardening.

The present invention will be described in more detail based on theexamples given below, but the present invention is not meant to belimited by these examples.

EXAMPLES Examples 1 to 4

(Synthesis of Acrylic-Series Copolymer A)

A copolymer was prepared by solution radical polymerization of 65 massparts of butyl acrylate, 25 mass parts of 2-hydroxyethyl acrylate, and10 mass parts of acrylic acid, as raw materials. Then, to thethus-obtained copolymer, 2-isocyanatethyl methacrylate was addeddropwise and reacted therewith, to prepare a copolymer A. In thismanner, the amount of 2-isocyanatethyl methacrylate to be added dropwiseand the reaction time of the solution radical polymerization areproperly adjusted, to prepare copolymers A1 to A5, respectively, whichwere different in carbon-carbon double bond amounts and molecularweights.

(Preparation of a Wafer Adhering Adhesive Tape)

To the copolymers A1 to A5, a polyisocyanate compound (trade name:Coronet L, produced by Japan Polyurethane) as a hardening agent, andα-hydroxycyclohexyl phenyl ketone as a photo polymerization initiatorwere admixed in a mixing ratio, as shown in the following Table 1, tothereby obtain a radiation-curable removable adhesive, respectively.

Each of the removable adhesives was coated on a high-densitypolyethylene resin film (100 μm) such that the removable adhesivethickness after drying would be 10 μm, to prepare an adhesive tape,respectively. Each of these adhesive tapes and a film-like adhesive (fordie bonding) mainly composed of an epoxy resin with 25-μm thickness werelaminated at a room temperature, to prepare respective wafer-adheringadhesive tapes of Examples 1 to 4 and Comparative Example 1, as shown inTable 1.

(Properties Test)

As for the following properties 1 to 6 of the thus-prepared waferadhering adhesive tapes, tests were carried out as described below. Thetest results are also shown in Table 1.

1. Gel Fraction

About 0.05 g of the removable adhesive layer was weighed, dipped in 50ml of xylene for 24 hours at 120° C., then the resultant xylene wasfiltered through a stainless-steel metallic net of 200 meshes andinsoluble constituents on the metallic net were dried for 120 minutes at110° C. Then, the mass of the dried insoluble constituents was weighted,to estimate the gel fraction by the formula shown below:Gel Fraction (%)=(Mass of insoluble constituents/Mass of weighedremovable adhesive layer)×1002. Removable Adhesive Double Bond Amount

The amount of carbon-carbon double bond contained in about 10 g of theheated and dried removable adhesive was measured and quantitativelydetermined by a mass increasing method by bromine addition reaction in adark place in vacuo.

3. Expandability (Interval Between Elements)

The above-prepared wafer-adhering adhesive tape was heat adhered to awafer for 10 seconds at 80° C., then a silicon wafer of a diameter of 5inches was full-cut into a size of 3 mm×3 mm, and the thus-cut wafer wassubjected to ultraviolet-radiation hardening (irradiation not on apattern shape but on the entire wafer). Then, the resultant wafer wasstretched in a wafer expanding machine (air pressure: 2.0 kg/cm²), andthe lengths of element intervals in longitudinal and transversedirections upon being stretched were measured, to estimate the averagevalues. The lengths of element intervals included a blade thickness of40 μm upon dicing.

The expandability is evaluated as below, based on the size (q) ofelement interval.

“◯”: q 100 μm: Image recognition of the element can be carried outsatisfactorily.

“Δ”: 100 μm>q 80 μm: It is difficult to carry out image recognition ofthe element.

“×”: q<80 μm: It is impossible to carry out image recognition of theelement.

4. Picking-up Success Ratio

The above-prepared wafer-adhering adhesive tape was heat adhered to awafer for 10 seconds at 80° C., and then diced-to 10 mm×10 mm.Afterwards, ultraviolet rays of 200 mJ/cm² were irradiated to theremovable adhesive layer by an air-cooling-type high-pressure mercurylamp (80 W/cm, irradiation distance: 10 cm). Then a picking-up test wascarried out by a die bonder machine (produced by NEC Machinery, tradename: CPS-100 FM), to obtain a picking-up success ratio at 100 picked-upchips.

5. Peeling Ability (Peeling Force)

Peeling ability before and after UV irradiation were measured accordingto JIS Z0237 (UV irradiation amount: 1000 mJ/cm²). The wafer-adheringadhesive tape was heat adhered to a mirror surface of a silicon waferheated to 80° C., and then the peeling force between the die-bondingadhesive layer and the adhesive tape was measured. The test was carriedout under the conditions of a peeling angle of 90° and a peeling speedof 50 mm/min.

6. Storage Stability

The above-prepared wafer-adhering adhesive tape was heat adhered to awafer for 10 seconds at 80° C., and diced to 10 mm×10 mm. Afterwards,ultraviolet rays of 200 mJ/cm² were irradiated to the removable adhesivelayer by an air-cooling-type high-pressure mercury lamp (80 W/cm,irradiation distance: 10 cm). Then, after the thus-irradiatedwafer-adhering adhesive tape was stood for 2 weeks under roomtemperature conditions (25° C., 60% RH), the picking-up success ratiowas obtained. Storage stability is evaluated and shown with thispicking-up success ratio (%). TABLE 1 Example Example Example ExampleComparative 1 2 3 4 Example 1 Kind of copolymer A1 A2 A3 A4 A5 Acidvalue (mgKOH/g) 5.9 5.6 6.9 5.0 6.0 Hydroxyl group value (mgKOH/g) 55 3440 34 50 Amount of copolymer to be used 100 100 100 100 100 (mass parts)Amount of hardening agent to be used 2 3 1.5 2 3 (mass parts) Amount ofphoto polymerization 1 1 1 1 1 initiator to be used (mass parts) Gelfraction (%) 90.5 91.3 68.2 86.7 50.8 Removable adhesive double bond 0.61.5 1.1 2.4 1.5 amount (meq/g) Expandability (element interval) ◯ ◯ ◯ Δ◯ Picking-up success ratio (%) 100 100 100 100 100 Peeling abilitybefore UV irradiation 1.20 1.31 1.29 1.13 1.34 (N/25 mm) Peeling abilityafter UV irradiation 0.21 0.11 0.16 0.14 0.21 (N/25 mm) Storagestability (%) 100 100 100 100 54

As can be seen from Table 1, Examples 1 to 3 according to the presentinvention showed that, in addition to that both of the picking-upsuccess ratio and the storage stability were each 100%, theexpandability was also good. Further, Example 4 indicated that theelement interval upon expansion was slightly poor, but the picking-upsuccess ratio and the storage stability were each 100%. Contrary tothese, Comparative Example 1 showed that the storage stability wasconspicuously poor.

From these results, it can be understood that the wafer-adheringadhesive tape of the present invention can be used as a dicing tape upondicing, and it can be used with the adhesive layer easily peeled offupon mounting, to thereby enable a direct die-bonding, and that theinventive wafer-adhering adhesive tape is excellent in storagestability.

Separately, an example of the wafer-adhering adhesive tape, in which theratio of a carbon-carbon double bond contained in the radiation-curableremovable adhesive layer was too low, was prepared and tested in thesame manner as Example 1, excepted that the ratio of carbon-carbondouble bond was changed to 0.3 meq/g. As a result, the picking-upsuccess ratio obtained in this example was 25%. At this time, thepeeling forces before and after UV irradiation were 1.42 N/25 mm and 0.4N/25 mm, respectively.

Example 5

The removable adhesive same as that in Example 1 was coated on ahigh-density polyethylene resin film (thickness: 100 μm) such that theadhesive thickness after drying would be 10 μm, to prepare an adhesivetape. Separately, a silicon wafer of 5-inch diameter, on which a surfaceprotective tape for grinding was attached, was provided. To a groundsurface of the wafer, on which surface no protective tape was attached,a film-like adhesive (for die bonding) with 25-μm thickness was heatadhered for 10 seconds at 80° C. The above-prepared adhesive tape wasattached to a (die-bonding) adhesive layer attached to the wafer. Then,the resultant silicon wafer adhered with the adhesive tape was subjectedto heat treatment for 100 seconds at 60° C., to peel off the surfaceprotective tape from the wafer.

Afterwards, in the same manner as to Example 1, this silicon wafer wasfull-cut into a size of 3 mm×3 mm, UV-irradiation hardened, andexpanded, and then subjected to the picking-up test. As a result, goodexpandability and picking-up property, as in Example 1, were exhibited.Further, it was found that the storage stability of the adhesive tapewas also good.

As seen from above, when a die-bonding sheet is heat adhered to a waferin advance and then the adhesive tape of the present invention isadhered and laminated to the resultant die-bonding adhesive layerattached to the wafer, the adhesive tape of the present invention canalso be preferably used.

INDUSTRIAL APPLICABILITY

The wafer-adhering adhesive tape of the present invention is preferable,for example, as a semiconductor wafer-adhering adhesive tape that isused in an adhering process for fixing a wafer or the like, dicing it,and lap-jointing it with a substrate or a semiconductor chip, when asemiconductor device, such as a silicon wafer or the like, ismanufactured.

Having described our invention as related to the present embodiments, itis our intention that the invention not be limited by any of the detailsof the description, unless otherwise specified, but rather be construedbroadly within its spirit and scope as set out in the accompanyingclaims.

1. A wafer-adhering adhesive tape, having a radiation-curable removableadhesive layer on a surface of a base, wherein the radiation-curableremovable adhesive layer is mainly composed of an acrylic-seriescopolymer having, in a principal chain, at least a radiation-curablecarbon-carbon double bond containing group, a hydroxyl group, and agroup containing a carboxyl group, respectively, and saidradiation-curable removable adhesive layer has a gel fraction of 60% orgreater.
 2. A wafer-adhering adhesive tape having a radiation-curableremovable adhesive layer and a die-bonding adhesive layer, in thisorder, on a surface of a base, wherein the radiation-curable removableadhesive layer is mainly composed of an acrylic-series copolymer having,in a principal chain, at least a radiation-curable carbon-carbon doublebond containing group, a hydroxyl group, and a group containing acarboxyl group, respectively, and said radiation-curable removableadhesive layer has a gel fraction of 60% or greater.
 3. Thewafer-adhering adhesive tape according to claim 1 or 2, wherein theratio of carbon-carbon double bonds contained in the radiation-curableremovable adhesive layer is 0.5 to 2.0 meq/g.